2021 – Page 28 – CNC Machining & Turning, Milling, Metal parts

Causes of computer gong limit alarm

Cause analysis of positive and negative hard limit alarm of computer gong

Computer gong processing in normal circumstances will not appear this alarm, but what is the reason for this situation?

The contact of travel switch is pressed and stuck (over travel);
The travel switch is damaged;
There is open circuit, short circuit and no signal source in the travel switch circuit;
The limit stop cannot press the switch contact to the action position;
The PLC input point is burnt out.

Many times, due to the improper use of the operation and technical personnel, or the work handover is not in place, there will be some failures in the processing of computer gongs. How can we prevent the deformation of parts in the processing of computer gongs?

In order to meet the requirements of ultra-high speed machining, the computer gong machining will adopt the structure of spindle motor and machine tool spindle, which realizes the integration of variable frequency motor and machine tool spindle. The bearing of spindle motor adopts magnetic floating bearing, hydrodynamic bearing or ceramic rolling bearing. Deformation often occurs in the process of processing, how to prevent it?

1、 In order to reduce the influence of cutting force and cutting heat, the deformation caused by rough machining can be corrected in finish machining.

2、 In order to reduce the influence of clamping force, the following measures are taken to reduce the influence of clamping force

When radial clamping is used, the clamping force should not be concentrated on a radial section of the workpiece, but should be distributed over a larger area to reduce the clamping force per unit area of the workpiece.
The position of clamping force should be selected in the part with strong rigidity to improve the deformation of thin-walled parts under the action of clamping force.
Change the direction of clamping force, change the radial clamping to axial clamping.
In order to reduce the clamping deformation, the computer gong processes the process boss or thread to strengthen the rigidity of the workpiece. When processing, the special structure claw is used to clamp, and the convex edge is cut off at the end of processing.

Introduction of CNC computer gong

Fuselage part:

1) Casting, which is the most important part of the computer gong, directly affects the accuracy, stability, wear resistance of the computer gong and the service life of the machine tool. After the casting is finished, it is not immediately used in the production. The good casting is that it is after wind and rain, sun exposure, natural weathering, and some of them are soaked in sea water. After the casting does not change, it is taken to the processing. The machine tool made in this way is not easy to change, and can maintain the stability and accuracy of the machine tool for a long time.

2) Spindle, the spindle is used to directly face the workpiece, it is driven by the motor to work, high-speed rotation, the spindle is equipped with a tool handle, it can chip the workpiece, meet various production needs, the quality of the spindle will directly affect the processing accuracy, if the internal bearing is worn, it is easy to cause the swing of the spindle, the accuracy of the processed things naturally has a few deviations . At present, the rotation speed of the main shaft is generally about 8000 rpm, and the high-speed machine can achieve more than 20000 rpm, and each machine has only one main shaft.

3) The screw rod is also a part of the fuselage. It is driven by a servo motor and drives the displacement of the worktable through the copper sleeve of the screw rod to meet the processing needs. If there is a gap in the screw rod, it is also directly reflected in the processing accuracy and finish.

4) There are two kinds of motors: servo motor and frequency conversion motor. The servo motor has good stability, high power of spindle drive motor and low coordination rate of three-axis drive motor.

5) The coupling is installed between the screw rod and the motor, which is just a linkage function.

6) The lubrication cooling system consists of an automatic oil pump, a spindle oil cooler and a chip liquid circulation system. When the machine tool is working, the oil can be pumped once every few minutes, and the oil pipe is connected to every corner, such as screw rod, guide rail, etc. if the oil circuit is blocked, the guide rail will be easily worn and the accuracy will be affected. Spindle oil cooling is a circulating cooling system added to cool the spindle. It is necessary or not for the spindle with 8000 revolutions, and it must be equipped for the spindle with more than 8000 revolutions. In the chip liquid circulation system, the oil in the oil tank is pumped up by the oil pumping motor and flushed to the workpiece being processed.

7) Sheet metal, sheet metal requirements are not too high, as long as there is no oil leakage on the line, but also involves the appearance of beautiful, image problems.

In order to improve the service life of stamping die or plastic die (including injection die, extrusion die, blow mold, etc.), the relevant parts of die cavity are generally made of high-strength wear-resistant materials (such as various grades of alloy structural steel, alloy tool steel and stainless steel, etc.), which have high hardness after heat treatment and are difficult to be machined by conventional machining Methods to process. For decades, the best way to deal with this kind of difficult to machine materials is to use special machining.

Discussion on precision mold processing technology

Since its invention in Europe in 1920s, fine blanking technology has experienced more than 80 years. It is one of the most important precision plastic forming methods in the field of thick plate manufacturing. It is a method with high technical content and good economic benefits for the economic production of large quantities, high quality, multi-functional ferrous and non-ferrous metal parts. Fine blanking press completes a stamping process, through the processing of special fine blanking die, one or more high precision forming parts can be produced, which can be directly used for assembly. It has been widely used in the fields of electronics, computer, electric power, home appliances, automobile and aviation. According to incomplete statistics, there are about 4500 fine blanking machines and 10000 parts produced in 40 countries in the world. For example, there are nearly 100 kinds of fine blanking parts in a car (car), including gearbox fork, seat and seat belt angle adjuster, planetary gear, brake shoe and steel back.

China’s fine blanking die technology has made great progress in the Eleventh Five Year Plan period, and has made a series of scientific research achievements in fine blanking process, materials, fine blanking press, die base, die and lubrication. As of the end of 2008, nearly 20 provinces and cities in China have professional fine blanking production equipment, with more than 80 fine blanking presses (excluding hydraulic mold base), more than 5000 fine blanking employees, producing about 2000 kinds of fine blanking parts, and a number of independent fine blanking mold development demonstration bases have been formed. Metal materials are expanded from non-ferrous metal blanking to ferrous metal blanking. The blanking thickness of low carbon steel, low alloy steel and stainless steel can reach 12mm; the blanking thickness of non-ferrous metals such as aluminum alloy and copper alloy can reach 18mm; with the progress of die materials and treatment methods, as well as the spheroidization process of the punched plate Some hard high carbon steel, high alloy steel and other low toughness materials such as nickel base or cobalt base alloy materials are also used in the production of fine blanking parts. In addition, the proportion of self-developed progressive compound fine blanking die, transfer die and modular die in domestic fine blanking die has increased significantly, especially the progressive compound fine blanking die for complex parts of automobile transmission system has basically realized localization.

The research, development and application of finite element numerical simulation technology, structure optimization technology of fine blanking die, intelligent design and knowledge base technology of fine blanking die improve and enrich the technical connotation of fine blanking die in China. However, at present, the fine blanking enterprises are generally small in scale, scattered in resources, low in production efficiency, shortage of talents and incomplete in supporting. Although in the fine blanking die development has a certain development ability.

How to prevent wear of CNC parts

The common wear types in machining include running in wear, hard grain wear, surface fatigue wear, thermal wear, phase change wear and hydrodynamic wear.

Running in wear is a kind of wear under normal load, speed and lubrication, which develops slowly and has little effect on machining quality in a short time.

Hard grain wear is due to the parts themselves or from the outside into the machine tool hard particles, mixed into the processing area, by mechanical cutting or grinding, causing damage to the parts, which has a serious impact on the processing quality.

Surface fatigue wear is a kind of mechanical damage caused by micro cracks or pits under alternating load. This kind of wear is usually closely related to the pressure, load characteristics, parts material, size and other factors.

Hot wear is the heat generated in the friction process, which makes the parts soften and wrinkle. This kind of wear usually occurs in high-speed and high-pressure sliding friction, the destructive wear is relatively large, and accompanied by the nature of accident wear.

Corrosion wear is a kind of chemical action, that is, chemical corrosion causes wear. When the part surface contacts with acid, alkali, salt liquid or harmful gas, it will be subject to chemical erosion, or the part surface combines with oxygen to form hard and brittle metal oxide which is easy to fall off and wear the part.

Phase transformation wear is a kind of wear caused by long-term work at high temperature, the grain of metal structure on the surface of the part becomes larger when heated, and the grain boundary is oxidized, resulting in a small gap, which makes the part fragile and wear resistance decreased.

Hydrodynamic wear is caused by the impact of liquid or particles mixed in liquid on the surface of parts at a faster velocity.

CNC computer gong machining center code

The meaning of letters in NC program

O: Program number

N: Program segment number, set program sequence number

G: Preparation function

X / Y / Z: dimension character, axis movement command

A / B / C / U / V / W: additional axis movement command

R: Arc radius

I / J / K: arc center coordinates (vector)

F: Feed, set feed rate

S: Spindle speed, set the spindle speed

T: Tool function, set tool number

M: Auxiliary function, on / off control function

H / D: tool offset number, set tool offset number

P / X: delay, set delay time

P: Program number instruction, set subroutine serial number (such as subroutine call: m98p1000)

50: Repeat, set the repeat times of subroutine or fixed cycle (e.g. M98 P1000 L2, omitting L for L1)

P / w / R / Q: parameters, parameters of fixed circulation (e.g. tapping g98 / (G99) g84 x)_ Y_ R_ Z_ P_ F_)

Explanation of common G code

G00: positioning or rapid movement

G01: linear interpolation

G02: arc interpolation / helix interpolation CW

G03: circular interpolation / spiral interpolation CCW

G04: dwell time or delay time

For example: G04 X1000 (or G04 x1.0)

G04 P1000 stands for 1 second

G09: accurate stop or accurate stop check (check whether it is within the target range)

G10: programmable data input

G17: select xpyp plane XP: X axis or its parallel axis

G18: select zpxp plane YP: Y axis or its parallel axis

G19: select ypzp plane ZP: Z axis or its parallel axis

G20: Inch input

G21: mm input

G28: return to reference point detection

Format: G91 / (G90) G28 x__ Y__ Z__

Passing through the middle point x__ Y__ Z__ Return reference point (absolute value / increment value instruction)

G29: return from reference point

G91/(G90) G29 X__ Y__ Z__

From the starting point through the reference point back to the target point X__ Y__ Z__ Instruction (absolute value / increment value instruction)

G30 returns to reference points 2, 3, 4

G91/(G90) G30 P2 X__ Y__ Z__ Return to the second reference point (P2 may be omitted). )

G91/(G90) G30 P3 X__ Y__ Z__ ; return to the third reference point

G91/(G90) G30 P4 X__ Y__ Z__ ; return to the fourth reference point

X__ Y__ Z__ : through the middle point position (absolute value / incremental value instruction)

G40: tool radius compensation cancelled

G41: left tool radius compensation (along the feed direction, the tool is on the left side)

G42: right tool radius compensation (the tool is on the right along the feed direction)

G43: tool length compensation + direction

G44: tool length compensation – direction

G49: cancel tool length compensation

CNC computer gong Processing Cam Parts

Research on key technology of design and manufacture of continuous fine blanking die for complex parts

Continuous fine stamping die for complex parts is the frontier basic technology of precision punching technology. It is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.

Study on the life promotion of fine blanking die and its related key technologies

Die life is a comprehensive reflection of the level of mold materials, small arts and supporting products. Taking the life of precision punching die as the leading point to solve the problem of too low life of precision die, it can not only solve the problem of too low life of the die in China, but also promote the development of die materials, fine blanking technology and supporting tooling and other auxiliary products.

Research and development of fine blanking precision forging composite technology

Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging precision stamping composite process is to find the combination points of these two processes (such as gear parts with hub and cam parts with short shaft). However, precision forging in China has a long history and has a high level. It is a good way to improve the overall level of precision punching technology in China.

CNC computer gong processing mechanical structure

1、 Analysis from the angle of numerical control

The CNC milling center requires a general speed for the CNC system, and the spindle speed is about 0 ~ 8000rpm
The engraving and milling machine requires a high-speed numerical control system, and the spindle speed is about 3000 ~ 30000 rpm
High speed cutting machine tools require high-speed CNC system and excellent servo motor characteristics. The spindle speed is about 1500 ~ 30000 rpm

2、 Analysis on programming software

In terms of software, standard CAD / CAM software such as MasterCAM Cimatron PE UG can be used in CNC milling centers, high-speed cutting machines and engraving and milling machines. Milling machine usually thinks Cimatron tool path is better. The new software fully studies the uniformity of cutting amount at every moment of the tool, especially the speed and smoothness of the moment when the tool enters and leaves the work, as well as the following error at the inflection point, which makes the results and design graphics more close to each other. In the CAD part, the intuitive three-dimensional solid modeling, such as SolidWorks, has been widely used And then transfer it to CAM software for processing through Igs.

But don’t worry, the development speed of CAD / CAM is much faster than that of CNC machine tools.

Because of the particularity of its cutting tool, engraving process has quite small angle control, so type3 is better.

3、 – requirements for automatic tool change and automatic tool setting of tool magazine

Machining center is a decent term, machining center is to complete a variety of processes in the automatic state of numerical control equipment, mainly for some fixed mass production operations, if we process a box with many holes and teeth, and have to do almost every day, what good way to improve efficiency, do not use the tool library, and will not cause artificial tool change error, there is only one way Automatic tool setting system, one tool is installed upward, one button, automatic tool setting, direct processing, the error is within 0.001 ~ 0.0003 μ m, compared with the automatic time change, the efficiency is not a bit slow. If it is a machining center without automatic tool setting device, the efficiency of the latter is much higher than that of the former. Note that the price of the best brand of automatic tool setting instrument, such as MARPOSS, is only about 10000 yuan, and it is unlikely to be damaged. In this way, if we fully consider the utilization value of capital, we must not use machining center equipment. In addition, there are many problems in the tool magazine of domestic manufacturers.

The processing method of CNC machine tool

There are two main forms of NC lathe processing in production and processing,

They are solid heat treatment and melt heat treatment. There is a certain difference between the two ways to make precision hardware processing parts. What’s more, they use different steel to make different workpieces. CNC lathe is composed of bed, headstock, turret feed system, cooling and lubrication system and CNC system. Different from the ordinary lathe, the feed system of CNC lathe is qualitatively different from that of ordinary lathe,

It does not have the traditional tool box, slide box and change gear frame, but directly uses servo motor or stepper motor to drive slide and tool through ball screw to realize feed movement. The NC system consists of NC unit, input and output module and operation panel. (1) Solid solution strengthening: because the solute atoms enter into the gap or node of the solvent lattice, the lattice will be distorted and the hardness and strength of the solid solution will increase. This phenomenon is called solid solution strengthening. 2. Compound: a new crystal solid structure with metallic properties is formed by the combination of alloy components.

Mechanical mixture: an alloy consisting of two crystal structures. Although it has two kinds of crystals, it is a component with independent mechanical properties.

Ferrite: interstitial solid solution of carbon in a-Fe (body centered cubic iron).
Austenite: interstitial solid solution of carbon in g-fe.
Cementite: stable compound (Fe3C) formed by carbon and iron.
Pearlite: a mechanical mixture of ferrite and cementite (F + Fe3C contains 0.8% carbon)
Ledeburite: a mechanical mixture of cementite and austenite (containing 4.3% carbon) Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endows or improves the performance of the workpiece by changing the microstructure inside the workpiece or the chemical composition on the surface of the workpiece.

How to add four and five axes to CNC computer gongs

CNC computer gong is a typical set of high-tech machining equipment, its development represents the level of a country’s manufacturing industry, has been highly valued at home and abroad.

Compared with general CNC machine tools, CNC computer gong has the following outstanding features:

All CNC computer gongs are equipped with protective doors. When processing, closing the protective doors can effectively prevent personal injury accidents.
The CNC computer gong generally has multiple feed axes (more than three axes) and even multiple spindles, and the number of linkage axes is also very large, such as three-axis linkage, five axis linkage, seven axis linkage and so on. Therefore, it can actively complete the processing of multiple planes and multiple viewpoints, and finish the high-precision processing of messy parts. The CNC computer gong can finish milling, boring, drilling, expanding, reaming, tapping and other processing with high concentration.
The CNC computer gong is equipped with a tool magazine and an active tool changing device,

Before machining, the required tools are loaded into the tool magazine, and the tools can be replaced actively through program control during machining.

The use of multiple worktables, worktable active exchange CNC computer gong processing, if with active exchange worktable, can end a worktable in the processing together, another worktable finish workpiece clamping, and then greatly shorten the auxiliary time, improve the processing power.
CNC computer gongs can be used for turning and grinding. For example, the circular worktable can drive the workpiece to rotate at high speed, and the cutting tool can only do the main motion without feeding. This makes CNC computer gongs have a wider processing scale
CNC computer gongs with high initiative, high precision and high power have high spindle speed, feed speed and rapid positioning accuracy. Through reasonable selection of cutting parameters, they can fully show the cutting performance of cutting tools and reduce cutting time. All kinds of auxiliary actions are fast and active, which reduces auxiliary action time and downtime. Therefore, CNC computer gongs are very popular The production power is very high.
High investment due to the high degree of intelligence, disordered structure and powerful function of CNC computer gong, the one-time investment and maintenance cost of CNC computer gong is much higher than that of ordinary machine tools.
In the appropriate conditions, the ability to perform the best benefits, that is, in the process of using the performance of the advantages of CNC machine tools, ability to fully reflect the benefits, which is very important for the rational use of CNC computer gongs.

Function introduction of engraving and milling machine

In terms of appearance and volume:

The volume of machining center is the largest, the volume of large 1690 machine is 4m * 3M, and that of small 850 machine is 2.5m * 2.5m; carving and milling machine is the second, and that of large 750 machine is 2.2m * 2m; carving machine is the smallest.

In terms of mechanical structure:

Machining centers generally use cantilever type, carving and milling machines and carving machines generally use gantry type structure, gantry type is divided into pillar type and fixed beam type, at present, carving and milling machines are mostly fixed beam type.

In terms of index data:

Spindle maximum speed (R / min): 8000 machining center; carving and milling machine is the most common 240000, high-speed machine is the lowest 30000; engraving machine is generally the same as carving and milling machine, engraving machine for high gloss processing can reach 80000, but it is not ordinary motorized spindle, but air floating spindle.

Spindle power: machining center is the largest, from thousands of watts to tens of kilowatts; carving and milling machine is the second, generally within ten kilowatts; carving machine is the smallest.

Cutting capacity: machining center is the largest, especially suitable for heavy cutting, roughing; carving and milling machine is the second, suitable for finishing; carving machine is the smallest. Engraving and milling machine

Speed: because the engraving and milling machine and engraving machine are relatively light, their moving speed and feed speed are faster than the machining center, especially the high-speed machine equipped with linear motor, the maximum moving speed can reach 120m / min

Accuracy: the accuracy of the three is almost the same.

From the processing dimension: the area of the worktable can better reflect this. The smallest worktable area (unit mm, the same below) of domestic machining center (computer gong) is 830 * 500 (850 machines); the largest worktable area of engraving and milling machine is 700 * 620 (750 machines), and the smallest is 450 * 450 (400 machines); engraving machine generally does not exceed 450 * 450, the common is 45 * 270 (250 machines).

In terms of application objects: machining center is used to complete the processing equipment of large amount of milling work pieces, large molds and materials with relatively high hardness, which is also suitable for roughening of ordinary molds; engraving and milling machine is used to complete the finishing of small amount of milling work pieces and small molds, which is suitable for copper and graphite processing; low-end engraving machine is inclined to wood, two-color board, acrylic board and other materials with low hardness Plate processing, high-end suitable for wafer, metal shell polishing.

It is generally believed that machining centers and engraving and milling machines can be used for both products and molds, while engraving machines can only be used for products.